Field of the Invention
Aspects of the present disclosure generally relate to information processing and, more particularly, to an information processing apparatus, an information processing method, a storage medium, and a technique for obtaining a correspondence relationship between a camera and a projector.
Description of the Related Art
There is widely known a three-dimensional measurement apparatus that obtains the three-dimensional coordinates of a measurement target object according the principle of triangulation by projecting pattern light from a projector onto the measurement target object and causing an imaging apparatus to observe light reflected from the measurement target object so as to find a correspondence between projection coordinates and image coordinates. According to the three-dimensional measurement method of projecting pattern light and observing reflected light, in a case where the measurement target object is a black object or metal object with low diffuse reflectance, since the reflected light is weak, the observed luminance of the pattern light may decrease. Therefore, the three-dimensional measurement method is greatly affected by noise, such as shot noise, so that the correspondence between projection coordinates and image coordinates cannot be precisely obtained. Thus, the three-dimensional measurement accuracy may be reduced.
As one of methods for coping with this issue, Japanese Patent Application Laid-Open No. 2014-115264 discusses a method of reducing the influence of noise by lengthening the exposure time of a specific pattern to increase the observed luminance. Besides, Gupta, Mohit; Yin, Qi; Nayar, Shree K, Structured Light in Sunlight, ICCV, 2013 discusses a method of obtaining the observed luminance required for high-accuracy measurement by narrowing the spreading of light emitted by a projector to increase the intensity of illumination of pattern light. Furthermore, Gupta, Mohit; Agrawal, Amit; Veeraraghavan, Ashok; Narasimhan, Srinivasa G, Structured Light 3D Scanning in the Presence of Global Illumination, CVPR, 2011 discusses a method of performing high-precision three-dimensional measurement by improving contrast using a projection pattern composed only of a striped pattern with a predetermined width or more without involving a thin striped pattern, which is likely to lead to low contrast.
However, the method discussed in Japanese Patent Application Laid-Open No. 2014-115264 disadvantageously requires a long measurement time since the exposure time is lengthened. Furthermore, the method discussed in Gupta, Mohit; Yin, Qi; Nayar, Shree K, Structured Light in Sunlight, ICCV, 2013 disadvantageously narrows a measurement range since the range onto which a pattern light is projected is narrowed.